There have been known scanners, printers, photocopiers and multi-function devices having multiple functions including scanning, printing, photocopying and/or faxing, each of which includes: a platen, e.g. of transparent glass, for placing a document thereon; a reader unit including an image sensor arranged below the platen and to read an image of a document while moving below the platen; and an automatic document feeder (ADF) disposed above the reader unit and including a stationary image sensor for reading an image of a document being conveyed.
For the image reading apparatus having such movable and stationary image sensors, it is required to carry out shading correction before reading images on both the movable and stationary image sensors.
In this connection, there has been proposed a technique for performing white level correction (e.g., shading correction) by arranging a fixed abutment member having a slant surface in a position facing a stationary image sensor such that the stationary image sensor is configured to read a white reference formed on the abutment member.